I would suggest DIY or sewing(its a large part of goth fashion)Â
But if you really dead set on thrifting you should ask for  "dark elegant clothing" to get the easiest point across.Â
Also i gotta be honest goth outfits sometimes look like emo grandma clothing, so i suggest looking for some cardigans, long skirts, and flowy dark buttons ups.Â
And if your lucky to find a corset or a choker or anything like that be sure to snag that as quickly as possible.Â
(ï¼ ï¼¾â—¡ï¼¾)